Abstract
Alkaloids are a large cluster of molecules found in Mother Nature all over the world. They are all secondary compounds and collection of miscellaneous elements and biomolecules, derived from amino acids or from transamination. This diverse chemical group is categorized, based on the amino acids that deliver their nitrogen atom and part of their skeleton. Alkaloids from a similar origin or having the same basic nucleus may have dissimilar biosynthetic pathways and different biological activity. They are derived from l-phenylalanine, l-tyrosine, anthranilic acid or acetate, l-histidine, l-ornithine, nicotinic acid, and l-lysine. Apart from other types of alkaloids, indole, tropane, and isoquinoline alkaloids are very important. People from all over the world are using them in their everyday life. Alkaloids can also have an animal origin, which may be endogenous or exogenous. This chapter highlights the phytochemistry of the main representatives among the diverse group of alkaloids. This chapter also focuses on their extraction, purification, fractionation, identification, and quantification procedures. A fundamental understanding of the biological activity of important alkaloids is also highlighted in this chapter. With the potential of revealing new compounds and diverse pharmacological properties, alkaloids still embrace a great potential for the future of drug discovery.